The Internet provides access to a wide variety of resources. For example, video and/or audio files, as well as web pages for particular subjects or particular news articles are accessible over the Internet. Access to these resources presents opportunities for advertisements to be provided with these resources and search results pages that facilitate identification of these resources. For example, a web page (such as, a search results page) can include advertisement slots in which advertisements can be presented. These advertisements slots can be defined in the web page or defined for presentation with the web page, for example, in a pop-up window.
Some systems allow for grouping users into sets based on characteristics shared by users in the group (for example, content of web pages viewed by the users). Such sets can be exposed to content sponsors who can present content to all users in the group. For example, if a user in a set selects to view content provided by the content sponsor, then the content sponsor can redistribute similar content to the user and the set to which the user belongs.